1. Field of the Invention
The present invention relates to a jet, and more particularly, to a jet that can eject droplets of different sizes.
2. Description of Related Art
Currently, jets spraying droplets of different sizes are widely used to improve the combustion efficiency of fuel in engines, or to increase the selectivity of ink jet printing. For example, when ink jet printers can print documents by way of ink droplets that have differing sizes, they are better able to improve both color variability and printing speed.
Please refer to FIG. 1, which is a side view of a jet 10 according to a related art. The jet 10 is disclosed in U.S. Pat. No. 4,251,824; xe2x80x9cLiquid jet recording method with variable thermal viscosity modulationxe2x80x9d. The jet 10 uses a plurality of heat generating bodies disposed on an axis of a liquid chamber 12 to provide energy individually or in turn, and in doing so generates a plurality of foam formations 31xcx9c35 in different positions of the chamber 12 to eject droplets of different sizes for printing. Although the jet 10 can eject droplets of different sizes, there is an undesired characteristic in that the jet 10 also readily ejects satellite droplets. When the foam formations 31xcx9c35 force out droplets 40, a tail of a droplet 40 may become separated from its associated body, forming another droplet in the period of expansion and contraction of the foam formations 31xcx9c35. These separated droplets are called satellite droplets. The generation of such satellite drops causes printed documents to take on a fuzzy appearance, or a lessening of contrast. The satellite droplets generated by the jet 10 follow after the main droplets. When the jet 10 has a relative motion to a printed document, the satellite droplets are printed onto the document in positions to differ from those of their parent main droplets. Thus, the printing capability of the jet 10 is adversely affected by the satellite droplets.
U.S. Pat. Nos. 6,102,530 and 6,273,553 xe2x80x9cApparatus and method for using bubble as virtual valve in microinjector to eject fluidxe2x80x9d disclosed an apparatus and method for forming a bubble within a microchannel of a microinjector to function as a valve mechanism between the chamber and manifold. These patents have been assigned to Acer Communications and Multimedia, presently known as BenQ Corporation, which is also the assignee of the present application.
It is therefore a primary objective of the present invention to provide a jet which can eject droplets of different sizes without satellite droplets to solve the above-mentioned problem.
In a preferred embodiment, the present invention provides a jet which uses a bubble as a virtual valve to increase the resistance between a chamber and a manifold, or to interrupt flow communications between the chamber and the manifold. Another bubble is then used to squeeze fluid from the chamber. The jet is in flow communications with a reservoir, and comprises a substrate, an orifice layer and a plurality of nozzles. The substrate comprises a manifold, which is used to receive fluid from the reservoir. The orifice layer is disposed above the substrate so that a plurality of chambers are formed between the orifice layer and the substrate. Each of the nozzles comprises an orifice and at least three bubble generators. In the present invention, different bubble generators are driven selectively to generate two bubbles, leading to a plurality nozzles that jet droplets of different sizes from the orifice thereon.
These and other objectives of the present invention will no doubt become obvious to those of ordinary skill in the art after reading the following detailed description of the preferred embodiment, which is illustrated in the various figures and drawings.